1. Field of the Invention
The present invention relates to a sheet storage apparatus that stores conveyed sheets.
2. Description of the Related Art
Conventionally, an image forming apparatus is provided with a sheet storage apparatus and is arranged to discharge sheets, on which images have been formed sequentially from an image forming portion, to the sheet storage apparatus. For instance, U.S. Pat. No. 5,722,030 (Kato) discloses an image forming apparatus provided with a bin-moving type sorter having a plurality of bins capable of storing printed sheets movably in a vertical direction.
The plurality of bin trays goes up or down one by one as spiral cams, provided on both sides of the trays, rotate once.
Each sheet on which an image has been formed in the body of the image forming apparatus is sent to the sorter by a pair of discharge rollers and is selectively sent in a direction of a sort path or a non-sort path by a change-over member. A sheet that has passed through the non-sort path is discharged onto a non-sort tray. A sheet that has passed through the sort path is discharged by another pair of discharge rollers and is stored on one bin tray of the bin trays that go up and down in synchronism with the discharge of the sheet. The sheets stored on the bin tray are aligned by an aligning bar that penetrates through cutaways provided in each bin tray and moves in a direction of a width of the sheet orthogonal to a direction in which the sheet is discharged. The sheets also undergo a stapling process carried out by an electrically-driven stapler as necessary.
The sheet storage apparatus of the image forming apparatus described above stacks and stores the sheets sequentially and flatly on the bin trays substantially horizontally disposed or gently inclined. Thus, the sheet storage apparatus has a layered structure of the plurality of bin trays, with the bin tray being changed per job of the discharged sheet and securely discriminating the discharged sheets. However, because the bin trays are positioned at different heights, visibility of the sheets stored in the low bin tray is not good and it is inconvenient to take the sheets out of the low bin trays in particular.
Furthermore, the sheets discharged onto the bin trays are not bundled in the stacked state, except in the case when the sheets are stapled as a bundle. As a result, there is a case when the sheets are disordered on the bin tray depending on a condition, e.g., curling, surface friction, and others, of the sheets during the discharge, or when one touches another sheet bundle by mistake in taking out the sheets out of the bin tray.